1. Field of the Invention
The present invention relates to an in-line film forming apparatus which perform film forming processing while a substrate serving as an object to be film-formed is sequentially conveyed between a plurality of film forming chambers and a manufacturing method of a magnetic recording medium using the in-line film forming apparatus.
2. Description of Related Art
In recent years, in the field of magnetic recording media used for hard disk devices or the like, the improvement in recording density is remarkable. Particularly, these days, recording density continues to increase at an amazing speed of about 100 times every ten years.
Such a magnetic recording medium has, for example, a structure on which a seed film, a underlayer film, a magnetic recording film, a protective film, and a lubricant film are sequentially laminated on both surfaces or one surface of a nonmagnetic substrate, and is generally manufactured using an in-line film forming apparatus which performs film forming processing while a substrate serving as an object to be film-formed is sequentially conveyed between a plurality of film forming chambers.
Meanwhile, in the in-line film forming apparatus, for example, a conveyor mechanism which conveys a carrier by magnetic attraction with magnets provided on the side of a carrier and magnets provided on the side of a film forming chamber is suggested as a method of conveying the carrier holding a substrate (see Patent Document 1).
Specifically, a conveyor mechanism which conveys the carrier by arranging a plurality of magnets so that an N pole and an S pole are alternately aligned at a lower part of the carrier, arranging along a conveying path a rotary magnet in which an N pole and an S pole are spirally and alternately aligned below the magnets, and rotating the rotary magnet around an axis while the magnets on the side of the carrier and the rotary magnet in non-contact are combined magnetically is described in Patent Document 1.
However, in the conveyor mechanism described in Patent Document 1, when the rotary magnet is rotated upward with respect to the lower surface of the carrier, the carrier may be lifted upward by the attractive force between both magnets and the carrier may vibrate greatly. On the other hand, when the rotary magnet is rotated downward with respect to the lower surface of the carrier, the carrier may be pushed against bearings holding the carrier, and movement of the carrier may worsen.
In order to solve such a problem, a method of guiding the carrier by bearings or the like so that the carrier does not move upward, or increasing number of downward bearings can be considered. However, when the number of bearings holding the carrier increases, there is a possibility that movement of the carrier may worsen or the degree of vacuum of a film forming chamber may deteriorate due to degassing from the bearings.
Additionally, it is desirable that a vacuum pump acting as a heavy load is arranged in the lower portion of a film forming chamber. However, when the rotary magnet and a drive mechanism which rotate the rotary magnet are set in the lower portion of the film forming chamber, they may cover an exhaust pipe connected to the vacuum pump, and exhaust by the vacuum pump within the film forming chamber may be obstructed.
Additionally, in manufacturing a magnetic recording medium using the in-line film forming apparatus, increasing the conveyance speed of the carrier is required in order to enhance production capacity. However, since the conveyor mechanism described in the above Patent Document 1 has a limit on increasing the rotating speed of the rotary magnet, it is difficult to increase the conveyance speed of the carrier.
Additionally, in the conveyor mechanism described in the above Patent Document 1, it is necessary to prevent the carrier from falling under its own weight through the use of the bearings. However, since it is difficult to use fluid lubricant on the bearings to be used in a vacuum, the rotation characteristic of the bearings worsens when a large load is applied to the bearings. Accordingly, in this case, it is difficult to move the carrier at a high speed.
Additionally, in order to increase the degree of vacuum within the film forming chamber, it is desirable to arrange the rotary magnet and its drive mechanism outside the film forming chamber. However, the inner structure within a film forming apparatus becomes complicated, and it becomes difficult to secure a high degree of vacuum in the film forming chamber due to leakage from the mechanism and its sealing parts.
In addition, as a method of conveying the carrier, using a linear motor is also suggested in order to improve the capability of a conveyance system of a disc substrate (see Patent Document 2).    Patent Document 1: Japanese Patent Unexamined Publication No. 2002-288888.    Patent Document 2: Japanese Patent Unexamined Publication No. Hei 8-335620.